The overall goal of the proposed research is imporvement in the prevention, therapy, and prognosis of bacterial meningitis. This condition remains a relatively common disease worldwide. Despite the introduction of newer antimicrobial agents and diagnostic techniques, the morbidity and mortality of bacterial meningitis remain unacceptably high. The two specific aims of this proposal are discrete, initimately related, and examine the alterations in blood-brain barrier (BBB) integrity induced by subarachnoid space (SAS) inflammation. The influence of bacterial meningitis on BBB permeability (BBBP) is poorly understood. We will determine the influence of surface characteristics (e.g. capsule, lipopolysaccharide [LPS]. fimbriae) of meningeal pathogens (e.g. E. coli, H, influenzae) and host factors (e.g. leukocytes, interleukin-1, tumor necrosis factor) on the traversal of 1125 I-albumin across the BBB in vivo and in vitro. The traversal of 125I- necrosis factor) on the traversal of 125I-albumin across the BBB in vivo and vitro. The traversal of 125I- albumin (normally excluded by the BBB) into the CSF in vivo during experimental meningitis and across an intact physiologically "tight" monolayer o cerebral capillary endothelial cells in tissue culture will be studied in parallel after exposure to the following substances: selected strains of H. influenzae type b (Hib) and E. coli to determine the role of capsul (e.g. Hib Rd-b+/02 vs Rd-/b/02; E. coli 018:K1:H7/9 vs 018:K5H7/11),LPS (Hib COL10vsCOL10p.v. vs COL10s.v.: E.coli 018:K1:H7/9 vs 01K1:H7/9and fimbriae (E.coli HB101 vs HB101 (pANN801-4)vsHB101(pANN801-13/TN5-32)respectively, purified Hib polyribosyl ribitol phosphate capsule, purified Hib LPS (classified vs D42,01,02, COL10, col10 p.v., COL10 s.v.). Hib outer membrane vesicles, human recombinant interleukin-I (riL-1beta), and human recombinant tumor necrosis factor (r-TNF-alpha) alone or in combination. These studies are symmetrical and complementaruy and reflect the influence of bacterial meningitis (and SAS inflammation) on precise, sensitive aspects of BBB function, critical to central nervous system (CNS) homeostatic mechanisms. The propensity for CNS invasion by specific micoorganisms is incompletely defined. We will determine the adhesion of selected strains (identical to those in specific aim 1) of H. influenzae and E. coli to rat cerebral capillary endothelial cells and chorid plexus epithelium in tissue culture in vitro under strictly standardized conditions. We will examine the influence of capsular polysaccharide, LPS, and fimbriae on adhesion to cerebral capillary endothelium and choroid plexus epithelium, the two major sites of the BBB. These studies on the affinity of bacteria for the components of the BBB are symmetrical and complementary to each other and the first specific aim, and are relevant to the initiation of meningitis and the neurotropism of meningeal pathogens. These two specific aims are closely related and examine microorganism-BBB interactions after, and before bacterial entry into the SAS, respectively.